1. Field of Invention
This invention provides a method and device to purvey an efficient, reliable and cost effective self cleaning disk filtration process.
2. Description of Prior Art
Modern industry and agriculture both require filtration technologies of varying capacities. Initially, innovative and higher efficiency filtration technologies evolved primarily out of the industrial market needs with agricultural filtration needs being satisfied by relatively simple and somewhat crude technologies. Concurrent with worldwide agricultural growth, and specifically as a consequence of the development of high efficiency drip tube irrigation technologies, the demand and consequential development of much more efficient, yet cost effective and reliable agricultural filtration processes burgeoned. Indeed, the previous trend of agricultural filtration technologies being primarily low cost derivatives of industrial designs has been superseded by the current industrial interest in employing modern agricultural derived technologies to industry. In many cases, adaptation of agricultural based filtration technologies into industrial applications have been positive and straight forward. Other industrial applications however, have encountered problems.
Disk filtration is one of the most promising of the filtration processes applied to the agricultural market. These agricultural based disk filtration technologies of the prior art however were fraught with problems and difficulties when applied to industrial service. The invention defined herein provides resolution to these problems and difficulties. As a point of fact, the new disk filtration technology defined herein defines superior performance for a majority of industrial filtration needs.
Disk filtration technology has been developed over many decades. There are generally two categories referenced in the art as disk filtration. One such category incorporates the parallel mounting of one or more disks comprised of a screening material encapsulating a substantially hollow plate-like structure which is generally mounted on a filtrate conduit. In such art, the filtration process occurs across the disk encapsulating screens wherein the screens may or may not include the provision of a filter aid coating such as diatomaceous earth. This subcategory of filtration technology has been commonly employed in industry for decades.
The second category of disk filtration has been developed primarily, though not exclusively, through agricultural needs. This category is the focus of this invention. This art embodies the employment of multiple ring-type disks, generally, though not always, made of a plastic material, stacked together to compose a primarily hollow cylindrical assemblage. Unfiltered water is forced, under pressure, to pass between these disks in a substantially radial direction, typically from the external to the internal side of the stack. Various types of protrusions or surface topology of the disks provide for the trammeling of particulate matter suspended in the fluid. Particle capture occurring upon the external surfaces of the cylindrical assemblage and/or upon the topologically rendered, adjacent contacting surfaces of the disks. Wherein for clarity, the trammeling surface external to the stack is substantially perpendicular to the direction of flow while that of the contacting surfaces is substantially coplanar with the direction of flow. The filtrate typically exits internal to the hollow disk stack and is ported from there to process for use.
The geometrical configuration and associated filtration mechanism of the disks as defined in the prior art are diverse. Reference is made to an early disk filter process wherein tapered disks with radial oriented internal filtrate porting was proposed for removal of a disperse sizing of particles is demonstrated in U.S. Pat. No. 1,643,299.
Other configurations practiced in the art are delineated in U.S. Pat. Nos. 2,847,126, 3,648,843, 3,827,568, 4,430,232, 4,707,259 and 4,726,900. In these practices perturbations and/or other spacing mechanisms are embodied on the disk surfaces so as to facilitate geometrical spacing between adjacent disks consistent with the required filtration size or grade. In such art the unfiltered water is constrained to pass radially between the disks of the cylindrical assemblage. Particles larger than the disk spacings therefore being trammeled upstream of the constrained fluid path. Various manifestations of this art have been further proposed in which an upstream configuration of the disks is so modified as to provide for an increased upstream surface lineage, thereby providing for an enhanced particle trammeling area. Reference is made to U.S. Pat. No. 4,410,430.
Further lessons of the art demonstrate an employment of surface grooves on one or both sides of the disks for the provision of flow channels between abutted disks. The size and geometry of said channels being the constraint on the passage of particles. Particles of sufficient size are trammeled at the entrance to the groove channels. References to these developments of the art are provided in U.S. Pat. Nos. 1,642,864 and 3,195,730.
As is compulsory with filtration processes in general, disk filtration processes require some means of filtration media surface cleansing to remove the collected solids separated from the treated fluid. Some examples of the prior art demonstrate little discussion of this issue. It can only be assumed that in these cases either disposal or disassembly and manual cleaning must be the procedure of choice. A drawback of disposal option is the expense of replacement. A disadvantage of disassembly and cleaning is the expense of labor and associated process downtime.
Prior art has evinced many examples in which the disks are cleaned through a mechanical means and/or hydraulic means. Such means being accomplished in automated, semi-automated or manually implemented processes. An example, cited in the prior art of a mechanical means for cleaning, demonstrates a procedure wherein the disks are rotated relative to one another providing a scraping mechanism and thereby facilitating removal of the collected debris. U.S. Pat. No. 1,926,557 as an example of such art. Detriments inherent in this application of the art are mechanical complexities involved in maintaining the proper relative disk orientations and the rotary mechanisms necessary to facilitate relative disk rotations. This example of the prior art also suffers from a detrimental tendency to smear or extrude rather than remove those collected solids which are soft and pliable.
Prior art has demonstrated other mechanical cleaning methods wherein brushes are employed to clean accumulated debris from the outer surface of a cylindrical filtration disk stack. Reference is made to U.S. Pat. No. 2,422,735 relating to such an invention. This example of the art suffers from mechanical complexity, high wear problems and fouling of the brushes.
Prior art has cited many examples of hydraulic cleaning processes. In these embodiments of the art, a washing liquid, generally filtrate, is directed to flush the collected solid debris from the disk stack. In the simplest form of the art, filtrate is forced to flow in a reverse manner through the filter with the aim of dislodging, separating and transporting collected solids from the filter. Solids entrained reverse flush waste fluid is then generally ported-aside for further processing or discharge.
An agricultural application in which such a reverse flow imbued cleaning process has found common use is irrigation system pre-filtration processes. In these applications, a plurality of filtration bodies containing disk filter stacks are operated in a parallel manner between a common inlet manifold and a common outlet manifold. Pressurized, unfiltered water passes from the inlet manifold through the filters, where solids are collected, and enters the slightly less pressured outlet manifold as filtrate for irrigation use.
Applications of such embodiments wherein an irrigation system and filtration process are so configured to facilitate reverse flowing pressurized filtrate from an outlet manifold for flushing of filters have been common. In these applications inlet flow to a chosen filtration body is diverted from communication with an inlet manifold to communication with a waste flush manifold. Pressure in the waste flush manifold is maintained at a level substantially lower than that of the outlet manifold. As a consequence of this pressure differential, filtrate from the outlet manifold flows in a reverse manner through the chosen filter body into the waste flush manifold. Solids collected in the chosen filter body are dislodged and conveyed, entrained within the reverse flowing stream, into the waste flush manifold for eventual discharge. Subsequent to cleaning, the filter is brought back into the filtration mode by restoration of communication to the inlet manifold and isolation from the waste flush manifold. The filtration system cleaning process then continues with sequential repetition of similar reverse flowing filtrate flushing on the remaining filter bodies in the system.
This embodiment of the art has historically found abundant applications, though it suffers substantially from inherent inadequacies in cleaning efficiency of the disk filtration surfaces. These inadequacies result from localized channeling of the flushing filtrate through isolated areas of the disk stacks as well as insufficient reverse flowing filtrate energy and associated cleaning activity to adequately dislodge solids adhering to the filtration surfaces. Consequently, such embodiments have proven to be labor intensive, requiring excessive maintenance for periodic manual cleaning of the filtration disk stacks. Mechanical failures and associated unreliability concerns are particularly prevalent and troublesome when the cleaning cycle frequency is high, as is a consequence of incomplete cleaning of the disks.
In response to the inadequacies of the simple reverse flowing filtrate flushing process, further developments of the art have been cited. To reduce channeling effects and to mechanically assist in dislodging solids adhered to disk filtration surfaces, several embodiments of the art have been cited wherein a filter disk cylindrical assemblage is decompressed and axially opened. In these embodiments an axial compressive force, which normally holds the disks tightly together, as a cylindrical stack during the filtration process, is removed in such a fashion that the filtration disk stack is substantially opened and the filtration disks rendered free floating in the axial direction. Reverse flowing filtrate is then directed through the open disk stack to flush collected solids debris from the opened and now accessible filtration surfaces. Upon completion of flushing, the disks are brought back together in compression and the filtration process resumed. Reference is made to U.S. Pat. Nos. 4,156,651, 4,402,829, 4,592,839 and 4,714,552 for examples cited of this art. These developments, though somewhat successful in improving the cleaning efficiency of the disks, still suffered from inadequate filtrate flushing energy and cleaning action upon the filtration surfaces of the disks.
Cleaning action in these examples of the prior art are burdened, especially within industrial applications, by an adherence of adjacent disks. As a result of collecting sticky or tacky solids between the disks, the disk elements will not separate when the compression force is removed for flushing. Accordingly, the filtration surfaces of these fused disks cannot be flushed. Frequent maintenance for manual cleaning is a necessity for many such industrial applications employing this prior art. As a result, such embodiments have proven to be labor intensive with an excessive amount of maintenance required for periodic manual cleaning of the filtration disk stacks. Mechanical failures and associated reliability concerns are particularly troublesome when the cleaning cycle frequency is high, as is a consequence of incomplete cleaning of the disks.
These embodiments of the prior art also suffer from failure of seals associated with disk stack compression and release mechanisms. These mechanisms require moving and sealing surfaces wherein sealing is necessary to provide isolation between the filtrate internal to the disk stack and the raw, dirty water external to the disk stack. As a consequence of a pressure differential between the internal filtrate side and external dirty water side of the filtration disk stack, dirt, grit and other detritus laden water tends to seep across the sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surface. As a consequence of the location and abrasive nature of this deposit; abrasion, scoring and eventual sealing failure occurs. Leakage results and filtrate quality is compromised. Accordingly, these embodiments of the prior art have proven to be both unreliable and maintenance intensive.
In response to unacceptable performance and excess maintenance requirements, further developments of the art have been advanced. Developments have been cited in which a directed flushing spray, of higher velocity than available in the earlier cited examples of the prior art, is directed over a relatively small area of filtration disk surfaces. As a consequence of the limited filtration disk area contacted by the directed spray, the spray and/or the cylindrical disk stack are mechanically maneuvered, relative to each other, so as to facilitate exposure and cleaning of the entire disk filtration stack surface by the directed spray. In several of these embodiments the directed spray is generated by a drafting or suction type of action across the filtration surfaces. To facilitate this action, filter environs, comprising an internal volume of a filter housing and an associated enclosed disk stack, are maintained at a pressure elevated above that of an external waste flush fluid manifold. A hollow, open ended or slotted conduit tube, which is in hydraulic communication with the waste flush manifold, is perpendicularly juxtaposed against a relatively small upstream area of the filter disk stack. In response to a pressure differential between the fluids constrained within the filter environs and the conduit tube, a converging spray is drafted past and through a relatively small area of the disk stack and into the open end or slot of the conduit. This induced flow dislodges, cleans and conveys collected solid debris from the disk filtration surfaces to the waste flush manifold for further processing or discharge. As a consequence of the limited area of the filtration surfaces contacted by the converging fluid, the open end or slot of the conduit tube and/or the cylindrical disk stack are mechanically maneuvered, relative to each other, so as to facilitate cleaning of the entire filtration surface. Such embodiments have been cited to also include mechanisms for decompression of the disk stack. This action, as was previously recited, promotes access to the disk filtration surfaces to ameliorate the cleaning process. Examples delineating these lessons of the art are referenced as U.S. Pat. Nos. 4,042,504, 4,045,345, 4,271,018, 4,295,963, 4,906,373 and 4,923,601.
A disadvantage associated with these examples of the art is an excess volume of waste flush fluid generated. In these examples the drafting action generates a convergence of flow from the filter environs. A substantial portion of the drafted fluid does not adequately contact the filtration surfaces to provide effective cleaning. Consequently, there is an excess volume of waste fluid generated. Flushing energy and cleaning action are also limited as a result of relatively small pressure differentials inciting the fluid to draft across the disk surfaces. Further, as previously discussed with other examples of the prior art wherein disk decompression occurs prior to flushing, these embodiments also suffer from seal failure and adhesion of adjacent disks.
Other examples of the prior art have been cited in which a flushing flow is delivered in the form of one or more pressured flushing sprays directed over relatively small areas of a filtration disk stack. Cited examples have professed sprays in several formats, one being wherein a high pressure flushing fluid is delivered from external of a filter to one or more spray nozzles incorporated onto an axially movable and rotatable conduit. In such embodiments, filtration flow is typically in a radial direction, external to internal through a hollow cylindrical stack of filtration disks. The spray nozzles are upon the conduit, which extends within the hollow cylinder of the filtration disk stack. The spray nozzles are so oriented as to facilitate a flushing spray, directed radially outwards, through the disk stack. Axial and rotational relative motion of the sprays across the disk stack occurs via axial and rotary motion of a section of the rigid conduit external to the filter. This motion provides spray contacting of the entire interior surfaces of the disk stack. Such embodiments have been cited to also include mechanisms for decompression of the disk stack. This action, as was previously recited, promotes access to the disk filtration surfaces to ameliorate the cleaning process. Examples of such embodiments can be referenced as U.S. Pat. Nos. 4,308,142, 4,655,910, 4,655,911, 4,906,357, 5,393,423 and 6,318,563.
Modifications manifest within these cited examples improve filtration performance on some industrial applications, though problems with disk adherence and plugging still exist within many industrial applications. These embodiments of the prior art also suffer from failure of seals associated with the movable conduit and seals associated with disk stack compression and release mechanisms. Conduit seals are necessary to provide isolation between pressured raw and dirty water internal to the filter and external environs of the filter.
As a consequence of a pressure differential between the filter external and internal environs, dirt, grit and other detritus laden water tends to seep across the sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surfaces. As a consequence of the location and abrasive nature of this deposit; scoring of the seal surfaces followed by leakage and sealing failure eventually occur. Similarly, these embodiments of the prior art also suffer from failure of seals associated with disk stack compression and release mechanisms. These mechanisms require moving and sealing surfaces wherein sealing is necessary to provide isolation between the filtrate internal to the disk stack and the raw, dirty water external to the disk stack. As a consequence of a pressure differential between the internal filtrate side and external dirty water side of the filtration disk stack, dirt, grit and other detritus laden water tends to seep across these sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surface. As a consequence of the location and abrasive nature of this deposit, abrasion, scoring and eventual sealing failure occurs. As a result, leakage occurs and filtrate quality is compromised. Because of these multiple sealing problems, these embodiments of the prior art have proven to be both unreliable as well as maintenance intensive. As a further disadvantage, the flushing sprays in these embodiments do not provide focusing means to maximize hydraulic energy and impact of the sprays as is necessary to adequately separate adhering disks and scour the filtration disk surfaces. These flushing sprays of the prior art do not provide and maintain sufficient energy and disk cleaning activity necessary for many industrial applications.
Another embodiment of the prior art citing disk flushing by directed sprays, employs the delivery of flushing fluid from external of a filter to a full circle spraying assembly via a conduit tube movably situated through a filter housing and internally extending axially into a filtration disk stack. Reference U.S. Pat. No. 4,156,651. In this embodiment, disk flushing is purveyed by a relatively thin circular, planar type spray, directed and impacting radially outward upon the disk surfaces. To facilitate full coverage of the disk stack during a flushing operation, the circular spraying assembly is extracted axially through the disk stack, as motivated by movement of the conduit, concurrent with full circle, radial spraying of flushing fluid through the disks. Such embodiments have been cited to also include mechanisms for decompression of the disk stack. This action, as was previously recited, promotes open access to the disk filtration surfaces to ameliorate the cleaning process. Developments manifest within this cited example improve filtration performance on some industrial applications, although problems with disk adherence and plugging still exist within many other industrial applications. This embodiment of the prior art also suffers from failure of seals associated with the movable conduit and seals associated with disk stack compression and release mechanisms. Conduit seals are necessary to provide isolation between pressured, dirty water internal to the filter and external environs of the filter. As a consequence of a pressure differential between the internal and external environs of the filter, dirt, grit and other detritus laden water tends to seep across these seals. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the seal. As a consequence of the location and abrasive nature of this deposit; scoring of the seal surfaces followed by leakage and sealing failure eventually occur. Similarly, this embodiment of the prior art also suffers from failure of seals associated with disk stack compression and release mechanisms. These mechanisms require moving and sealing surfaces wherein sealing is necessary to provide isolation between the filtrate internal to the disk stack and the raw, dirty water external to the disk stack. As a consequence of a pressure differential between the internal filtrate side and external dirty water side of the filtration disk stack, dirt, grit and other detritus laden water tends to seep across these sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surface. As a consequence of the location and abrasive nature of this deposit, abrasion, scoring and eventual sealing failure occurs. As a result, leakage occurs and filtrate quality is compromised. Because of these multiple sealing problems, these embodiments of the prior art have proven to be both unreliable as well as maintenance intensive. As a further disadvantage, the flushing sprays in these embodiments do not provide focusing means to maximize hydraulic energy and impact of the sprays as is necessary to adequately separate adhering disks and scour the filtration disk surfaces. The flushing sprays of this prior art do not provide and maintain sufficient energy and disk cleaning activity necessary for many industrial applications.
Further examples cited of the prior art, reference U.S. Pat. Nos. 4,655,910 and 4,655,911, exhibits the flushing efficiency of the directed spray approach, but eliminates much of the mechanical complexity associated with relative movement between the filtration disks and the directed sprays. In these embodiments, within a filter body, a filtration disk stack circumscribes a centralized, rigid element which is secured to the filter body on one end and freestanding on the other. This element is oriented in the axial direction of the disk stack and provides the rigid, lateral support necessary to maintain the cylindrical configuration of the filtration disk stack. An axially movable cap is supported on seal bearing surfaces at the free standing end of this element. When this cap is moved toward the secured end of the rigid element it compresses the filtration disk stack to facilitate filtration. When moved axially away from this position, the compression on the filtration disk stack is relieved and the disk stack is axially opened to facilitate flushing. Located on extended walls of this element are a series of spray nozzles so oriented as to equally impart a tangentially oriented spray upon the disks circumscribing the element. The secured end of the rigid element supports a critical flow check mechanism. During filtration this flow check mechanism directs filtrate flow from internal of the compressed disk stack to a filtrate discharge port exiting the filter. Upon reversing flow of filtrate back through this discharge port into the filter, the critical flow check mechanism directs the reverse flowing filtrate via hollow sections of the rigid element to lift the end cap, thereby decompressing the disk stack. Concurrently, reverse flowing filtrate is also conveyed through hollow sections of the rigid element to the spray nozzles for spray flushing the encircling disks. The similar tangential orientations of the sprays initiate a vigorous rotational spin of the disks about the rigid element. The multiple, axial placement of the spray nozzles and the rotational spin of the disks are intended to convey full flushing spray coverage of the disk stack.
The flow check mechanisms cited in these examples of the prior art have proven to be disadvantageous for several reasons. These flow check mechanisms engender a high pressure drop thereby purveying a substantial hindrance to flow through the filters. Accordingly additional filters and/or high pressure pumps must be employed to facilitate adequate flow. This is expensive and adds further operational complexity. Further, these flow check mechanisms have proven to be unreliable, sensitive to water treatment chemicals and maintenance intensive.
The performance of these embodiments of the prior art show some improvement over the previous lessons of the art, although in many industrial applications they still suffer from inadequate flushing energy and cleaning action upon the solids laden disk filtration surfaces. One specific inadequacy relates to voids of flushing spray upon the disks resulting from axial spacing gaps of the spray nozzles on the rigid element. As a result, the disk stack separates into a series of mini stacks of adhering disks. These disks adhere together because, as a result of spacing gaps between the spray nozzles on the rigid element, no spray impact occurs. These mini stacks are contacted by flush sprays only on the upper surface of the top disk of the mini stack and the lower surface of the bottom disk of the mini stack. Indeed, the presence of a top spray and a bottom spray only, with a void of spray in the middle of the mini stack, actually holds the affected disks together, hindering their separation for cleaning. Flushing efficiency of the sprays is further compromised by the similar orientation of the sprays. Each spray purveys a similar rotational impetus to the disk stack because of the similar tangential orientation of the sprays. Such rotation is intended to facilitate maximum spray coverage of the disk stacks. The disks are motivated by the sprays to rotate in the direction of the sprays. However, because of the common orientation of the sprays, these embodiments suffer from the generation of excessively high rotational speeds of the disks. As the rotational speed of the disks approach the velocity of the spray, the impact energy of the spray upon the disks approaches zero. Cleaning energy and efficiency drop dramatically and the disks do not flush clean.
These embodiments of the prior art employ the movable end cap to facilitate compression and decompression of the disks. The end cap slides down and up, respectively, on sliding sealing surfaces of the end cap and the rigid element. In these examples of the prior art, these sliding surfaces incorporate one or more seals to isolate the filtrate internal to the disk stack from the raw feed-water external to the disk stack. As a consequence of a pressure differential between the internal filtrate side and external dirty water side of the filtration disk stack, dirt, grit and other detritus laden water tends to seep across the sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surface. As a consequence of the location and abrasive nature of this deposition; abrasion, scoring and eventual sealing failure occurs and the filtrate quality is compromised. Accordingly, these embodiments of the prior art have proven to be unreliable and maintenance intensive.
A further disadvantage of these embodiments of the prior art relate to the configuration of the sprays. The spray nozzles incorporated therein generate a diverging, expanding spray which rapidly drops in energy as it exits the nozzles and contacts the disks. Accordingly the lower spray energies result in an inability for the spray to separate adhering disks as well as purveying an inferior cleansing action to those disks which have separated.
A further disadvantage of these embodiments of the prior art is the requirement of at least two, three-way valves or four, two way valves, externally mounted to a raw water inlet and filtrate outlet of the filters. These valves are necessary to facilitate filtration operations and reverse flushing operations. These valves are expensive, high maintenance mechanisms which are particularly prone to leakage and failure.
In a prior patent granted to this inventor, reference U.S. Pat. No. 6,752,920, there is presented a filter embodiment comprised of three body chambers. One chamber contains a filter disk stack with the internal region of the disk stack ported into a filtrate plenum chamber. The filtrate plenum chamber is ported for filtrate discharge from the filter. A third flush fluid receiving plenum chamber is provided to receive an externally supplied flushing fluid for cleaning the filter disks. The filter disk stack circumscribes several rigid hollow shafts. These shafts are oriented in the axial direction of the filter disk stack and provide lateral support necessary to maintain a cylindrical configuration of the filtration disk stack. Oriented on these shafts, adjacent to the disk stack, is a plurality of nozzle holes wherein a slight majority of the nozzles are configured tangentially in one direction while the remaining, slight minority of the nozzles, are oriented tangentially in an opposing direction. These nozzles provide hydraulic communication between the hollow interior and the exterior of the shafts. The lower ends of the shafts pass, in a rigid, sealed fashion, through the filtrate plenum cavity and terminate within, and in hydraulic communication with, the flush fluid receiving plenum of the filter. The hollow interior sections of these shafts provide a conduit for flow of the cleaning medium from the flush fluid receiving plenum to the nozzles. The ends of the hollow shafts opposite the flush fluid receiving plenum support an axially movable, combined inlet valve seat and disk compression assembly. This assembly moves axially toward the disk stack during filtration to facilitate compression of the disks. During flushing operations, this assembly moves in an axial direction away from the disk stack, thereby releasing the disks for flushing, while concurrently seating in and closing an inlet port to the filter. This assembly further supports a shaft which is directed axially opposite to the inlet valve seat and disk compression assembly and extends into the filtrate plenum. The free end of this shaft supports a block valve located within the plenum chamber. While in the filtration mode, the combined inlet valve seat and disk compression assembly is compressed against the disks and the shaft moves the block valve into an open position facilitating communication between the interior filtrate volume of the disk stack and the filtrate plenum. During flushing operations, the flushing fluid is introduced, under pressure, into the flush fluid receiving chamber. The pressured fluid moves through the hollow shafts supporting the disks and motivates the inlet valve seat and disk compression assembly away from the disks and into a sealing position on the inlet port. Concurrently, the flushing fluid expels from the nozzles and impacts, in a cleansing fashion, across the filtration surfaces of the disks. The disks rotate at a low speed in the direction imposed by the slight majority of the nozzles. The spray from these nozzles impacts the disks in a head on fashion thereby providing an optimum spray cleaning performance.
This embodiment of the art provides substantially improved cleaning performance as a result of multi-directional nozzle orientations, reduced pressure drop by not requiring any check valves and the ability to employ an exterior, higher pressure, source of cleaning fluid. Further, the disadvantages associated with the required inlet and outlet valves of the prior art are eliminated. Though the performance improvements heralded by this prior art of this inventor were extraordinary, several disadvantages still remained to be addressed. One of these problems was the adherence of adjacent disks due to sticky collected solids and the consequential inability to flush clean the closed disk surfaces. These problems relate to both the fore-mentioned void spaces on the disk stack resulting from rigidly mounted spray nozzles and from the reduced flushing energy associated with diverging sprays exiting the nozzles. Another disadvantage of this prior embodiment of the art by the inventor, is the unreliability and maintenance required of moving seals on the disk compression end cap assembly in the presence of abrasive solids in the raw feed-water to the filter. Another disadvantage is the requirement of a flush valve to control the inlet of flushing fluids. This valve must be of sufficient size to accommodate the high flow rates required for efficient flushing and cleaning of the disks. As a consequence, the size and cost of this valve is substantial. Further, if chemicals are employed in the flushing fluid, the materials of construction of this valve must be resistant to these normally harsh chemicals. Such exotic materials add substantially to the cost of the valve. The disadvantages of the flush valve in this prior art of the inventor are numerous.
Another disadvantage of this latest example of the prior art corresponds to sliding seals which are required in the movable valve seat and disk compression assembly. These sliding seals are necessary to separate the filtrate internal to the filtration disk stack from the dirty, pre-filtered water external to the filtration disk stack. As a consequence of a pressure differential between the internal filtrate side and external dirty water side of the filtration disk stack, dirt, grit and other detritus laden water tends to seep across the sealing surfaces. Inherent to this seepage is a deposition of dirt, grit and other detritus against the high pressure, dirty water side of the sealing surface. The location and abrasive nature of this deposit results in an eventual failure of the seals, thereby compromising the filtrate quality.
The disk flushing procedures of the prior art have generally employed filtrate for flushing operation. For those applications in which the available filtrate is of insufficient pressure, external pressurized filtrate or other flushing fluid sources have been employed. Applications of the prior art have employed municipal water, pump pressurized filtrate and compressed air sources in an air over water approach to develop pressure for flushing. High externally supplied pressures generally improve flushing performance however, frictional pressure losses internal to the filters, throttling pressure losses through valves, throttling pressure losses through flush nozzles and energy loss through diverging spray patterns all dramatically reduce the flushing energy exerted upon the solids laden disk filtration surfaces. As a consequence, in many industrial applications, the employment of these alternative high pressure flushing processes is still insufficient to provide satisfactory cleaning of the filtration surfaces. Consequently, to facilitate effective filtration disk cleaning in such circumstances, the filters of the prior art must be dismantled and the disks removed and chemically washed. This is a labor intensive, time consuming, costly and inefficient process.
A further disadvantage in the prior art relates to the inability to readily employ chemicals beneficial for cleaning of the filtration disks. Often in industrial applications, solids adhere to the disks with such tenacity that chemicals must be employed to adequately clean the filtration disks. In order to facilitate such cleaning, the filters of the prior art must be dismantled and the disks removed and chemically washed. This is a labor intensive, time consuming, costly and inefficient process.
Industrial applications often result in a deposition of solids upon the filtration disk surfaces which require elevated temperatures for effective cleaning. A disadvantage of the prior art is that there are no ready provisions to facilitate flushing of the filtration disks at elevated temperatures. Those industrial applications in which elevated temperatures are necessary for adequate filtration disk cleaning either require the employ of an isolated, heated, high pressure cleaning fluid source or dismantling of the filters, removal of the filtration disks and external washing of the filtration disks at an elevated temperature. This is a labor intensive, time consuming, costly and inefficient process.
In a similar fashion, there are many industrial applications wherein the only method for successful cleaning of the filtration disks requires cleaning with chemicals at elevated temperatures. The prior art teaches no ready options for this procedure other than flush fluids supplied by external, heated tankage or dismantling of the filter, removal and elevated temperature chemical cleaning of the filtration disks. This is a labor intensive, time consuming and inefficient process.
Another disadvantage of the prior art is biotic plugging and fouling of the filtration disks. This problem arises from biological growth developing on the filtration disk surfaces. This common problem presents a substantial impediment to cleaning of the filtration disks. Further, the problem continues even after apparently successful flushing as a consequence of the growth of residual biotic cultures remaining on the disks. There are no methods taught by the prior art to resolve these problem other than dismantling of the filter, removal, cleaning and sterilization of the disks and any other effected internal structures by chemical, thermal or combined means. This is a labor intensive, time consuming, costly and inefficient process.